Single and multiple-step electrochemical processes are useable to reduce metal-oxides to their corresponding metallic (unoxidized) state. Such processes are conventionally used to recover high purity metal, metals from an impure feed, and/or extract metals from their metal-oxide ores.
Multiple-step processes conventionally dissolve metal or ore into an electrolyte followed by an electrolytic decomposition or selective electro-transport step to recover unoxidized metal. For example, in the extraction of uranium from spent nuclear oxide fuels, a chemical reduction of the uranium oxide is performed at 650° C., using a reductant such as Li dissolved in molten LiCl, so as to produce uranium and Li2O. The solution is then subjected to electro-winning, where dissolved Li2O in the molten LiCl is electrolytically decomposed to regenerate Li. The uranium metal is prepared for further use, such as nuclear fuel in commercial nuclear reactors.
Single-step processes generally immerse a metal oxide in molten electrolyte, chosen to be compatible with the metal oxide, together with a cathode and anode. The cathode electrically contacts the metal oxide and, by charging the anode and cathode (and the metal oxide via the cathode), the metal oxide is reduced through electrolytic conversion and ion exchange through the molten electrolyte.
Single-step processes generally use fewer components and/or steps in handling and transfer of molten salts and metals, limit amounts of free-floating or excess reductant metal, have improved process control, and are compatible with a variety of metal oxides in various starting states/mixtures with higher-purity results compared to multi-step processes.